Ensure type checkers can correctly infer extension argument types

[philippjfr]

Seems like type checkers get confused about ParameterizedFunction signatures so we help them a little bit with a typing.overload.

Fixes #7690

[codecov]

Codecov Report

Attention: Patch coverage is 72.72727% with 3 lines in your changes missing coverage. Please review.

Project coverage is 87.08%. Comparing base (56d9055) to head (c96e252).
Report is 7 commits behind head on main.

Files with missing lines	Patch %	Lines
panel/config.py	72.72%	3 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #7709      +/-   ##
==========================================
+ Coverage   87.04%   87.08%   +0.04%     
==========================================
  Files         346      346              
  Lines       52625    52657      +32     
==========================================
+ Hits        45806    45858      +52     
+ Misses       6819     6799      -20     

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